The most stable Lewis acid–base adduct among the following is

Options

A. `H_(2)O to BCl_(3)`
B. `H_(2)S to BCl_(3)`
C. `H_(3)N to BCl_(3)`
D. `H_(3)O to BCl_(3)`

Explanation

To determine the most stable Lewis acid-base adduct among the given options, we need to analyze the Lewis acids and bases involved. Here’s a step-by-step solution:

### Step 1: Identify the Lewis Acids and Bases
Lewis acids are species that can accept an electron pair, while Lewis bases are species that can donate an electron pair. In the options provided, we need to identify which species act as Lewis acids and which act as Lewis bases.

### Step 2: Analyze the Basicity of the Compounds
Among the given compounds, we need to assess which one is the strongest Lewis base. The basicity can be determined by the availability of lone pairs and the electronegativity of the atoms involved.

- **Ammonia (NH₃)**: Has a lone pair on nitrogen, making it a strong Lewis base.
- **Water (H₂O)**: Also has lone pairs but is less basic than ammonia due to the higher electronegativity of oxygen.
- **Hydrogen sulfide (H₂S)**: Has lone pairs but is less basic than ammonia and water.
- **Sulfur dioxide (SO₂)**: Acts as a Lewis acid rather than a base in most reactions.

### Step 3: Determine the Stability of the Adducts
The stability of the Lewis acid-base adduct depends on the strength of the interaction between the Lewis acid and the Lewis base. The stronger the base, the more stable the adduct will be when it forms a bond with a Lewis acid.

- **Adduct of NH₃ with a Lewis acid (e.g., BCl₃)**: This is expected to be very stable due to the strong basicity of ammonia.
- **Adduct of H₂O with a Lewis acid**: Less stable than NH₃ adducts.
- **Adduct of H₂S with a Lewis acid**: Even less stable than H₂O adducts.
- **Adduct of SO₂**: Typically acts as a Lewis acid, so it doesn't form a stable adduct with a base.

### Step 4: Conclusion
Based on the analysis, the most stable Lewis acid-base adduct among the given options is the one formed by ammonia (NH₃) with a Lewis acid like BCl₃. Therefore, the correct answer is:

**Answer: Ammonia (NH₃) with BCl₃ is the most stable Lewis acid-base adduct.**